1. Field of the Invention
The present invention relates to a system for supporting live plant growth on building roofs and particularly to a self-contained modular system for retaining the plant growth independent of the underlying roof structure.
2. Description of Related Art
A green roof is a roof that is at least partially and usually substantially covered with vegetation. Green roofs can improve energy efficiency of buildings, reduce storm water run-offs and contribute to a healthier environment. Green roofs can also provide a mechanism to offset rising energy costs and address the constant demand for increased energy efficiency.
For example, urban heat island effect is used to describe urban air and surface temperatures that are higher than nearby rural areas. Typically, the urban surfaces such as pavement and rooftops tend to absorb solar energy and reradiate the energy as heat. This, in turn, raises temperatures which can negatively impact the environment by raising energy costs and creating adverse health conditions.
Green roofs are an effective counter-measure to offset at least a portion of the urban heat island effect. A green roof provides shade to the underlying roof and reduces temperature by cooling the air that surrounds the plants of the green roof. That is, the evapotranspiration experienced by the plants tends to reduce local temperatures, thereby reducing thermal loads on the buildings. In addition, the vegetation of a green roof can absorb rainfall and thus reduce storm water runoff that would otherwise collect pollutants and be drained into water supplies necessitating further treatment of the water runoff.
However, the need remains for a system for providing rooftop vegetation which can be maintained in an economical manner, without requiring retrofitting the structural design of the underlying building, or exposing the existing structure to detrimental effects of the vegetation.